1. Field of the Invention
This invention relates generally to electrical generators and more particularly to electrical generators located within pneumatic wheel assemblies.
2. Description of the Prior Art
It is sometimes useful to have a source of electricity located within a pneumatic wheel assembly. For example, telemetry units can be placed within a pneumatic wheel assembly to monitor and transmit data including tire pressure, vehicle speed, temperature, flexure, etc. If a vehicle operator places any reliance on a telemetry unit it is imperative that the unit be supplied with a reliable source of electricity.
There are a number of prior art patents which describe electrical generators that can be disposed within a pneumatic wheel assembly. For example, in U.S. Pat. No. 3,699,367 a mechanism for obtaining energy from tire flexure is described that includes a plunger assembly radially attached to a wheel. As the wheel rotates, an end of the plunger is depressed by the normal flexure of the wheel's tire as it comes into ground engagement. The reciprocating motion of the plunger drives a generator. A device operating on similar principles is described in U.S. Pat. No. 3,760,351.
While the above mentioned inventions perform their functions admirably, they both include mechanisms to convert the linear motion of the reciprocating plungers to the rotary motion needed to drive a generator's armature. Such linear-to-rotary converters reduce the overall efficiency of the device and add components that can wear and fail with age.
When a generator of any type rotates with the wheel to which it is attached it is subjected to large centrifugal forces. Furthermore, since a telemetry unit usually rotates with the generator, it too is subjected to large forces.